That's possibly the biggest lesson from the closely watched contest to fill the remainder of Gifford's term in Arizona's 8th Congressional District.

After the assassination attempt against Giffords in January 2011, after her resignation to focus on her recovery in January 2012, you could have been forgiven for thinking the race between Democratic ex-Giffords aide Ron Barber and repeat Republican nominee Jesse Kelly would hinge on stewardship of "Gabby's seat," a Republican-leaning, Tucson-based border district in southeastern Arizona, and stand somewhat removed from the rancorous moods of national politics.

Instead, the campaign has focused relentlessly on Social Security and Medicare, Kelly's tea party ties, and Barber's relationship with President Obama and House Democratic leader Nancy Pelosi, the same hallmarks of partisan skirmishes across the country stretching back into the last election cycle.

Private polling by both sides has shown a close, margin-of-error race in the 8th District for weeks. Spending by outside groups and the two campaigns has reached around $4 million, and people in the district describe an unceasing drumbeat of campaign commercials on TV. That has contributed to a remarkable level of awareness and early voting turnout for a special election; more than 120,000 early ballots have been returned so far, and observers expect around two-thirds or more of the total vote to be cast early. Republicans have underperformed their registration advantage in the early ballot returns, perhaps giving an edge to Barber and Democrats, who sometimes struggle to turn out their voters in special elections.

Apart from the decline of local politics, the other big lesson from this race will be a look at which party's message appears to be having more impact in the final live test before November's general election. In a way, the special election's local angle ended up making a nationalized race appealing to both sides. For the Republicans' part, the strong resonance of Barber's Giffords connection made nationalizing the race the most effective way to oppose him. And Democrats figured that Barber was already so closely identified with Giffords that there was no point in hitting voters over the head with it -- she hasn't appeared in any of Barber's television advertisements, though she did appear at a Barber rally this weekend. Instead, Democrats saw an opportunity to test-drive messaging on entitlements that they feel would be effective against other Republicans nationwide, in the type of district Democrats need to take back the House majority.

Kelly and outside GOP groups have connected Barber to Obama and Pelosi in virtually every ad and campaign appearance, reprising their most effective line from 2010. That line has caused Barber some discomfort in the campaign, especially in one debate where he briefly vacillated on whether he supported Obama for reelection. On the policy side, while touting lower taxes and fewer regulations, Republicans have used the national Democratic connection to hit Barber for Medicare cuts in "Obamacare" and potential energy cost increases under a cap and trade system, two other critiques pulled straight from the successes of 2010.

Barber's campaign presented him as a moderate former businessman, by contrast, and while he has talked up those credentials on the air, outside Democratic groups and his campaign have hammered Kelly as a candidate out of the mainstream. The most memorable ad of the special came from Democratic-aligned House Majority PAC, which played clipsof Kelly saying the minimum wage should be eliminated and calling Social Security and Medicare a "Ponzi scheme," and, for the cherry on top, included video of Kelly saying, in 2010, that Giffords was not a "hometown hero" -- even though it was plucked from the 2010 campaign, before Giffords was shot, in the present context, nothing is further outside the mainstream.

Kelly has reinvented himself somewhat in the special election campaign, foregoing the strident Tea Party-infused rhetoric of 2010 and earlier positions on privatizing Social Security, among other things. But Democrats have mined Kelly's statements from the nasty 2010 campaign with Giffords and are using them all against him this year, another tactic Democrats think can be replicated against some other Republican incumbents and repeat candidates across the country in the fall.

In general, people tend to over-read the broader impact of special elections for House seats. A Democratic hold in the 8th District would not necessarily signal a renaissance for the party, nor would a GOP victory mean that Republicans would look likely to add seats in November. (For one thing, the redistricted version of the district gets more Democratic for the fall election.) But the district's makeup -- slightly Republican-leaning and senior-heavy, with a historical moderate streak -- makes it an interesting bellwether for the ongoing messaging war between the parties, especially on Social Security and Medicare.

Ultimately, the Giffords factor and the district's Republican lean give both parties reason to hope for victory, to rationalize defeat, and to not overreact too much about either result. A loss would not condemn either party's chances in November, though losing such a symbolic district would be an especially bitter defeat for Democrats. The great prize Tuesday, apart from the seat in Congress, is a large-scale test result of the parties' messaging. Whichever side emerges as the winner will have a better sense of what they have to do to appeal to the residents of other swing districts for the rest of the cycle.